Tuning fork drive for clocks

ABSTRACT

A timepiece is provided with a drive mechanism comprises a tuning fork having an electromagnetic oscillator located between the bight thereof, energized by an electronic amplifying system connected to a battery source of current. One tine of the tuning fork is magnetically connected to a spoked gearwheel forming in combination therewith an escapement mechanism for the timepiece. The other tine is provided with a permanent magnet extending transversely to the direction of oscillation and which cooperates with a magnetic polar piece to create an isochronous compensator for the tuning fork.

I United States Patent [151 3,638,416 I Kaltenbach [451 Feb. 1, "13772 [54] TUNING FORK DRIVE FOR CLOCKS 3,207,965 9/1965 Lavet ..58/23 TF X [72] Inventor: Klaus Kaltenbach, Triberg" Germany 3,338,047 8/1967 Kueffer ..58/23 TF [73] Assignee: Flrma Jahresunhren-Fabrik Gmbl-l, Aug. FOREIGN PATENTS OR APPLICATIONS Schall & some, Triberg, Black Forest 704,477 2/1965 Canada ..58/23 TF Germany 22 Fl (1: A 13 1970 Primary Examiner-Richard B. Wilkinson 1 l e pr Assistant Examiner-Edith C. Simmons PP 27,470 Attorney-Richard Low and Murray Schaffer [30] Foreign Application Priority Data [57] ABSTRACT A timepiece is provided with a drive mechanism comprises a 1969 Germany 19 795'9 tuning fork having an electromagnetic oscillator located 52] U S Cl 58/23 TF 310/37 between the bight thereof, energized by an electronic amplify- [51] In. .Cl 66 3/00 g system Connected to a battery Source of current one tine [58] Fieid TF H 6 of the tuning fork is magnetically connected to a spoked 58/ll6 gearwheel forming in combination therewith an escapement mechanism for the timepiece. The other tine is provided with [56] References Cited a permanent magnet extending transversely to the direction of oscillation and which cooperates with a magnetic polar piece UNITED STATES PATENTS to create an isochronous compensator for the tuning fork. 2,743,614 5/1956 Clifford ..74/1.5

8 Claims, 3 Drawing Figures PATENTED FEB Have mmvron K LFr U5 KflLTEA/BA H TUNING FORK DRIVE FOR CLOCKS BACKGROUND OF THE INVENTION The present invention relates to battery-operated timepieces and in particular to clocks and watches employing electronically controlled electromagnetic drive means.

In such devices the escapement mechanism is driven by a tuning fork oscillated by an electromagnetic assembly comprising a pair of spool or wire coils each having a permanently magnetized core. The assembly is located between the tines of the fork and the coils connected to an electronic amplifier which derives an energizing signal from the battery or other source of voltage. On energization of the electromagnetic assembly the tuning fork is caused to vibrate and its oscillations transmitted to the escapement mechanism to run the timepiece.

It is known that when the tuning fork is impressed with a signal having a frequency greater than 300 lHz., it combines with the escapement mechanism to accurately drive the timepiece no matter what signal variations occur. However, when the frequency on the tuning fork falls below this level, as when the battery or source of energy decreases in voltage or its circuitry changes the operating characteristics due to wearing or other features, the isochronism between the respective parts is adversely affected and the operating oscillating amplitude of the tuning fork fails to be truly representative of the frequency change. As a result the regulation and accuracy of the timepiece is severely affected. This is a particularly significant drawback in the operation of the battery driven clocks especially when the frequency falls to a level between 30 and 300 Hz.

It is an object of the present invention to provide a drive mechanism for timepieces overcoming the noted drawback.

It is a particular object of the present invention to provide a drive mechanism for a timepiece employing an electronically controlled electromagnetically operated tuning fork in which a decrease in oscillating frequency is automatically compensated.

It is another object of the present invention to provide an isochronous compensating mechanism for a tuning fork drive mechanism assuring efiicient regulation of the timepiece.

These objects as well as other together with numerous advantages will be illustrated in the following description.

SUMMARY OF INVENTION According to the present invention a timepiece is provided with a drive mechanism comprises a tuning fork having an electromagnetic oscillator located between the bright thereof, energized by an electronic amplifying system connected to a battery source of current. One tine of the tuning fork is magnetically connected to a spoked gearwheel forming in combination therewith an escapement mechanism for the timepiece. The other tine is provided with a permanent magnet extending transversely to the direction of oscillation and which cooperates with a magnetic polar piece to create an isochronous compensator for the tuning fork.

In the preferred form of the invention the first mentioned tine of the tuning fork also includes a permanent magnet extending transversely to the direction of oscillation and is similar to and symmetrically arranged on the tuning fork relative to the electromagnet of the isochronous compensator. It is also preferred that the supporting member for the permanent magnets be made of nonmagnetic material and be located at the end of the tine.

A full description of the structure of the present invention follows herein.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view partially sectioned and in schematic form of the tuning fork drive mechanism of the present invention,

FIG. 2 is a section through the wound coils and permanent magnets forming the electromagnetic oscillating mechanism for the tuning fork, and

FIG. 3 is an enlarged, inverted and reversed, section of the polar member of the present invention.

DESCRIPTION OF INVENTION In the embodiment ofthe invention shown in the figures, the device comprises a tuning fork having a pair of tines l1 and 12 between the bight of which is located a pair of wire wound spools l3 and 14, one of which comprising the driving electromagnetic coil the other comprising the control or pickup electromagnet coil. The tine ll cooperates with a switch or escapement mechanism generally numbered 15 while the other tine l2 cooperates with an isochronous oscillating compensating mechanism generally depicted by numeral 16.

The electromagnetic devices 13 and 14 are seen in detail in FIG. 2 and comprise a cantilevered wire wound outer coil body, in each of which is coaxially located a permanent magnet 27 and 28 respectively. The magnets 27 and 28 are placed with their polarities in opposed directions and are axially located within the wire spools with one of their cross-sectional faces abutting against a portion of the interior windings of the spool. The windings overlap the ends of the core members 27 and 28 so that when mounted between the tines of the tuning fork the cores do not come in contact with the respective tines and provide efficient oscillatory energy to the tines without interference or feedback. The wire wound spools l3 and 14 are connected to an electronic amplifier which is itself connected to a source of current such as a battery. Neither the electronic amplifier, the battery or the connecting circuitry are shown in the drawings since each is conventional in this art and will be well known to those skilled therein.

The escapement mechanism comprises a spoked wheel 25 made of highly magnetic material mounted about a rotatable axle secured within the body or frame of the timepiece. Aligned in parallel with the axis of the wheel 25 is a permanent magnet 17 which is adjustably secured within a nonmagnetic holder 18 located in pendulum fashion at the end of the tine 11. The holder 18 may also be adjustably secured to the end of the tine. The permanent magnet 17 is generally cylindrical in shape and of the bar type and has an outer end cooperating with the spoked wheel 25. The permanent magnet 17 is clamped in any usual manner within a slot in the holder 18 so that it may be adjustably secured in its extended position. The spoked wheel 25 and the permanent magnet 17 cooperate between them to provide a magnetic switch or escapement mechanism which on oscillation of the tine 11 causes the wheel 25 to rotate.

The isochronous compensating mechanism associated with the other tine 12 comprises a polar piece 19 made of highly magnetic material in the shape ofa right angle. One leg of the right angle member is positioned adjacent the upper end of the tine l2 and extends in the plane normal to the vertical run of the tine. This portion forms a pole shoe in which is formed a slot 26. Mounted at the end of the tine I2 is a nonmagnetic holder 21 similar to the holder I8 holding the permanent magnet 17. The nonmagnetic holder 21 is also provided with a slot in which is adjustably clamped a permanent magnet 20 similar to that of the previously mentioned magnet 17. The permanent magnet 20 extends into the slot 26 of the pole shoe formed by the pole piece 19. The axis of the slot 26 extends positioned generally along the axis of the magnet 20. It is noted that both support 18 and 21 and the extending bar magnets l7 and 20 are similar, and are symmetrically located at the ends of the tines with respect to a longitudinal central axis passing through the center of the tuning fork.

The pole piece 19 is mounted by its vertical portion to a vertical supporting plate 22 as seen in FIG. 3. (Note that FIG. 3 is an inverted and reversed view of the portion shown in FIG. I.) This support 22 is provided with a slot and a screw 23 which extends through and into engagement with the vertical portion of the pole piece 19. By adjusting the screw 23 the symmetrical position of the pole piece along the axis of the cooperating magnet 20 is easily obtained. A second screw 24 extends into a bore in the support 22 and abuts against the pole piece 19 securing the pole piece against any movement.

When placing the device in operation the gap formed by the slot 26 in the pole piece 19 is so arranged with respect to the permanent magnet 20 by adjustment of the screws 23 and 24, that with even a varying battery potential (i.e., between 1.6 volts and 1.1 volt) the tuning fork will be caused to oscillate with a uniform frequency. The final tuning of the fork, at its correct frequency, is made by merely positioning the mass formed by the permanent magnet 20 and its holder 21 toward and away with respect to the end of tine 12.

When the electromagnetic oscillators l3 and 14 of the tuning fork are then connected to the electronic amplifying device the tuning fork is caused to resonate, working the permanent magnet 17 in conjunction with the spoked wheel 25 which then turns at the rate dictated by the frequency of the tuning fork. The effects of isochronism failure are automatically compensated for by the arrangement of the permanent magnet 20 at the end of the second tuning fork tine 12 which in cooperation with the highly magnetic pole piece corrects the amplitude of the oscillations causing the regular tuning fork resonating system to return to its initial predefined position.

The present invention provides a tuning fork drive mechanism particularly adaptable for frequencies under 300 Hz. and for example as low as 100 Hz. The apparatus is selfregulating even for small isochronous failures. Additionally the present device is simply constructed and can be made of component parts which in the main are similar to apparatus for driving the escapement mechanism. By symmetrically and similarly forming the various parts of the present device extraneous factors are eliminated in its operation.

The present description is intended as being illustrative only of the present device, since many modifications, changes and equivalent embodiments may be made.

What is claimed:

1. A drive mechanism for a timepiece comprising an electromagnetically oscillated tuning fork having a pair of tines, a magnetic escapement mechanism and a magnetic isochronous compensating device respectively associated with the tines of said tuning fork, means mounted on one tine and extending outwardly therefrom into cooperation with and providing the sole drive for said escapement mechanism, means mounted on the other tine and extending outwardly therefrom in sole cooperation with said isochronous compensating mechanism, said extending means cooperating to maintain said tuning fork in uniform frequency.

2. The drive according to claim 1, wherein each extending means comprises a permanent bar magnet and includes nonmagnetic holder means mounting said bar magnet to the end of each of the associated tines.

3. The drive according to claim 2, wherein each of said extending magnets are adjustably secured within said holder.

4. The drive according to claim 3, wherein each of said magnets and holders are similar and are symmetrically arranged on their associated tines with respect to the central axis of the tuning fork.

5. The drive according to claim 4, wherein the isochronous compensating device comprises a magnetic pole piece having a slot formed therein, said pole piece being suitably mounted with respect to its associated magnet and having the axis of said slot positioned along the axis of said extending magnet.

6. The drive according to claim 5, wherein the escapement mechanism comprises a magnetic wheel having a plurality of spokes extending about the circumference thereof, said spokes cooperating with the extending magnet associated with it so as to cause said wheel to turn on oscillation of said magnet.

7. The drive mechanism according to claim 1, wherein said tuning fork is driven by an electromagnetic assembly comprising a control and drive coil having a magnetic core, said magnetic core being located axially within said coil, said coil extending over each end of said core, said control and drive coils being located between the tines of said tuning fork.

8. The drive according to claim 7, wherein the magnetic cores are arranged with their poles extending in opposite directions. 

1. A drive mechanism for a timepiece comprising an electromagnetically oscillated tuning fork having a pair of tines, a magnetic escapement mechanism and a magnetic isochronous compensating device respectively associated with the tines of said tuning fork, means mounted on one tine and extending outwardly therefrom into cooperation with and providing the sole drive for said escapement mechanism, means mounted on the other tine and extending outwardly therefrom in sole cooperation with said isochronous compensating mechanism, said extending means cooperating to maintain said tuning fork in uniform frequency.
 2. The drive according to claim 1, wherein each extending means comprises a permanent bar magnet and includes nonmagnEtic holder means mounting said bar magnet to the end of each of the associated tines.
 3. The drive according to claim 2, wherein each of said extending magnets are adjustably secured within said holder.
 4. The drive according to claim 3, wherein each of said magnets and holders are similar and are symmetrically arranged on their associated tines with respect to the central axis of the tuning fork.
 5. The drive according to claim 4, wherein the isochronous compensating device comprises a magnetic pole piece having a slot formed therein, said pole piece being suitably mounted with respect to its associated magnet and having the axis of said slot positioned along the axis of said extending magnet.
 6. The drive according to claim 5, wherein the escapement mechanism comprises a magnetic wheel having a plurality of spokes extending about the circumference thereof, said spokes cooperating with the extending magnet associated with it so as to cause said wheel to turn on oscillation of said magnet.
 7. The drive mechanism according to claim 1, wherein said tuning fork is driven by an electromagnetic assembly comprising a control and drive coil having a magnetic core, said magnetic core being located axially within said coil, said coil extending over each end of said core, said control and drive coils being located between the tines of said tuning fork.
 8. The drive according to claim 7, wherein the magnetic cores are arranged with their poles extending in opposite directions. 